Method of performing sequential non-mechanical and mechanical machining operations along a common centerline

ABSTRACT

The disclosure relates to a method of drilling holes in difficulty machinable material wherein non-mechanical means, such as a laser or an electron beam, is used to drill a first undersize hole which is characterized by a surrounding recast area followed by a mechanical reaming operation to remove the recast area and produce a finished bore in the material which then reveals no metallurgical alteration.

Kle -121w 55R lO lO fZ KR 3 76969504 United States Patent Cupler, II

[451 Oct. 10,1972

[54] METHOD OF PERFORMING SEQUENTIAL NON-MECHANICAL AND MECHANICALMACHINING OPERATIONS ALONG A COMMON CENTERLINE [72] Inventor: John A.Cupler, H, 10 Cupler Drive, LaVale, Cumberland, Allegany County, Md.21502 [22] Filed: Aug. 11, 1971 [21] Appl. No.: 171,004

Related US. Application Data [63] Continuation of Ser. No. 800,237, Feb.18,

1969, abandoned, which is a continuation-inpart of Ser. No. 715,711,March 25, 1968, Pat. No. 3,478,419.

[52] US. Cl. ..29/558, 219/121 EB, 219/121 L, 264/25, 264/ 156, 408/1408/701, 408/704,

[51] Int. Cl. ..B23p 13/04 [58] Field of Search....29/558, 557; 219/121EB, 121 L; 331/945; 77/22, 25, 5; 460/1, 24, 701, 704,

[56] References Cited UNITED STATES PATENTS 1,703,232 2/1929 Gray et a1l48/12.1 2,844,706 7/1958 Lorenz ..2l9/69 3,265,855 8/1966 Norton..219/121 3,388,314 6/1968 Gould ..219/68 X 3,431,389 3/1969 Tudor et a1..219/121 3,440,388 4/1969 Otstot et al. ..2l9/69 OTHER PUBLICATIONSGas-Jet Lasar Cutting British Welding Journal, Aug. 8, 1967, pages 443-445.

Primary Examiner-John F. Campbell Assistant Examiner--Victor A. DiPalmaAttorney-Colton & Stone ABSTRACT The disclosure relates to a method ofdrilling holes in difficulty machinable material wherein non-mechanicalmeans, such as a laser or an electron beam, is used to drill a firstundersize hole which is characterized by a surrounding recast areafollowed by a mechanical reaming operation to remove the recast area andproduce a finished bore in the material which then reveals nometallurgical alteration.

PATENT'EDnm 10 I972 FIG. I

aaezzuk/fia FIG. 6

ATTORNEYS.

METHOD OF PERFORMING SEQUENTIAL NON- MECHANICAL AND MECHANICAL MACHININGOPERATIONS ALONG A COMMON CENTERLINE This application is a continuationof Ser. No. 800,237, filed Feb. 18, 1969, now abandoned, which in turnwas a continuation-in-part of, Ser. No. 715,711, filed Mar. 25, 1968,now U.S. Pat. No. 3,478,419.

The invention relates to methods of conducting machining operations and,more particularly, to methods of forming or drilling very smallprecision holes in difficulty machinable materials. Heretofore, it hasbeen extremely difficult, and in many instances impossible, tomechanically drill very small precision holes in certain of the newspace age alloys because of their extreme hardness and/or toughnesscoupled with the very small diameter drill such as, for example, in therange below 0.015 inch which would be required to drill such holes. Theknown problems attendant such drilling operations as regards shorteneddrill life generally as well as drill fatigue, drill breakage and drilldulling specifically are more fully pointed out in applicants copendingapplication, Ser. No. 786,344 entitled Method of Machining InvolvingProgressive Step Tool Change filed Oct. 23, 1968 now U.S. Pat. No.3,570,330.

It has been previously proposed to utilize recently developed beammachining techniques employing lasers or electron beams to performvarious machining operations on difficultly machinable materials. Onesuch proposed useage is the machining of very small holes in hollow gasturbine blades for air cooling purposes. Due to the extremeenvironmental conditions under which turbine blades operate,particularly as regards centrifugal forces and high temperatures, thenecessity for structural integrity of these blades is absolute. Eventhough turbine blades are normally cast from the most advanced alloys,the application of intense heat such as that generated by lasers andelectron beams will produce a metallurgical alteration of the metalimmediately adjacent the beam machined area. Such alteration is normallyreferred to as recast metal and is that whose metallurgical propertieshave been rendered inferior by the application of heat. Additionally,such metallurgical alterations are normally accompanied by hairlinecracks in the recast portion of the metal. These minute hairline crackswould not be critical in many instances but in those structures wherethe requirement for structural integrity is absolute, such as in turbineblades, they are considered to be fatal. The reason for this is thatunder the extreme operating conditions experienced in gas turbineengines the hairline cracks represent the weak points of the blade andthey frequently enlarge and extend until the blade fails. The failure ofa single turbine blade will virtually destroy the rotor section of anengine in which the failure occurs resulting in engine shut-down as wellas time consuming and expensive repairs. In the case of a single engineaircraft, the failure of a single turbine blade could, of course, resultin loss of the aircraft.

A primary object of the invention is to teach a method of machiningwherein the advantages of beam machining techniques may be employed in amanner such that the finished product is not metallurgically changed.

It is among the further objects of the invention to teach a method ofdrilling difficultly machinable materials utilizing a combination ofbeam and mechanical techniques that is far faster than previousmechanical drilling techniques and, yet, retains the advantages ofmechanical drilling as regards bore wall smoothness and lack ofmetallurgical changes in the metal being machined; and to insure thatthe mechanical and nonmechanical drilling operations are performedcoaxially.

These and other objects of the invention are achieved by the beamdrilling of a hole which is undersize in diameter as compared to thedesired finished hole and then mechanically reaming the beam drilledhole to the desired diameter while, concomitantly, removing themetallurgically changed material immediately surrounding the beamdrilled hole.

It is, of course, essential that the undersize beam drilled hole and themechanical reaming tool be coaxial. In order to insure this coaxialrelationship as well as to provide the relatively fast interchange ofbeam and mechanical drilling equipment that is essential from thestandpoint of operating economy; the automatic tool changer described inthe aforesaid copending application, Ser. No. 715,711 is advantageouslyutilized in the practice of the invention.

Concentricity of the beam drilled hole with the initial axis of rotationof the mechanical drilling tool is insured by virtue of rotating thebeam focussing equipment during the beam drilling operation.

The manner in which the foregoing and other objects are achieved willbecome more apparent from the ensuing description when considered inconjunction with the drawings, wherein:

FIG. 1 depicts, fragmentarily, an elevational view of an automatic toolchanger wherein a non-mechanical or beam drill is illustrated in workingposition and a mechanical drill is shown in non working positionrelative to a workpiece depicted in broken elevation;

FIG. 2 is a greatly enlarged showing of the nonmechanical or beam drillshown in FIG. 1;

FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. 2;

FIG. 4 is a greatly enlarged showing of the mechanical drill shown inFIG. 1;

FIG. 5 is a greatly enlarged fragmentary illustration of the workpieceshown in FIG. 1; and

FIG. 6 is a view similar to FIG. 2 illustrating the manner in whichrotation of the beam drill assures concentricity of the bore.

A non-mechanical tool or drill is herein defined as one which directs asource of energy toward a workpiece to perform a machining or drillingoperation as opposed to the physical engagement of the tool, itself,with the workpiece as in the case of a mechanical tool or drill.

In FIG. 1 is fragmentarily illustrated an automatic tool changer 10 ofthe type fully described in copending application, Ser. No. 715,711filed Mar. 25, 1968. Vee bearing 12 supports a non-mechanical tool ordrill 14in position to machine workpiece 16 supported by a conventionalworkholder 18. A mechanical drill 20 is shown in non-working position ontool rack 22 which is capable of interchanging tools 14 and 20 on Veebearing 12 in the manner fully described in the aforesaid copendingapplication.

Although the non-mechanical drill may assume many forms such aselectrodischarge machining, ultrasonic or grit blasting equipment; theinvention is primarily directed to the use of beam drilling equipmentwhich includes lasers and electron beams. While the invention isspecifically described with reference to a laser source and opticalfocussing equipment, it will be apparent that the conventional electronbeam source and electromagnetic focussing equipment may be substitutedtherefor.

A laser source 21 directs defocussed beam 26 through elongated openings28 in the hollow cylindrical non-mechanical tool 14 while the same isundergoing rotation by virtue of the engagement of drive belt 30 withdrive pulley 32 affixed to tool 14. As tool 14 is rotated, beam 26passes, sequentially, through the four openings 28 to impinge on one ofthe four faces of pyramidal mirror 34 and be reflected to focussing lens36 from whence the same passes through tool aperture 38 to workpiece 16.The workpiece is illustrated, in FIGS. 1 and 5, as having already beendrilled by the focussed laser beam to produce rough walled bore 40 andthe immediately surrounding recast area 42 containing hairline cracks 44which recast area and cracks are characteristics of beam machining ashas been previously explained.

Bore 40 is drilled undersize by the focussed laser beam and thereafterreamed by mechanical tool whose blade 46 removes recast area 42 toproduce a smooth walled bore of desired finished diameter indicated bythe phantom lines in FIGS. 1 and 5.

The fact that beam drilling tool 14 is rotated results in beam 26 beingpulsed as the unfocussed portion of the beam is broken by the solidportions of tool 14 intermediate the apertures 28. The pulsing of thebeam does not adversely affect its machining characteristics and therotation of the tool insures that the beam drilled hole will always becoaxial with the axis of tool rotation. This concept is illustrated inFIG. 6 wherein it may be seem that even through beam 26 may not becoincident with too] axis 48 the circular sweep of the beam, indicatedby dotted line 50, will insure that the bore thus drilled is coaxialwith axis 48.

Depending on whether the depth of bore 40 requires axial movement oftool 14, the same may be preprogrammed for axial infeed or not,independently of the necessary infeed of mechanical tool 20, in themanner explained in the aforesaid copending application. Apertures 28and mirror 34 are of such axial length as to insure that beam 26 mayimpinge on the mirror throughout the extent of reciprocating movementthat may be imparted to tool 14.

Iclaim:

l. A method of forming a finished diameter bore in a metallic workpiece,comprising; simultaneously forming an undersize bore in said workpieceand producing a metallurgically altered zone surrounding said undersizebore by beam machining said workpiece; and then concomitantly enlargingsaid undersize bore and removing said zone throughout the entire lengththereof by a rotary metal removal operation to produce said finisheddiameter bore.

2. The method of claim 1 wherein said beam machining consists of lasermachining.

3. The method of claim 1 wherein said beam machiningconsists of electronbeam machining.

. A method of machining a workpiece, comprising;

positioning a beam machining tool on a fixed tool support adjacent ametallic workpiece; beam machining said workpiece along a centerline tosimultaneously form an undersize bore and a metallurgically altered zonesurrounding said undersize bore; substituting a rotary metal removaltool on said fixed tool support for said beam machining tool; andmechanically machining said workpiece along said centerline toconcomitantly enlarge said undersize bore and remove said zonethroughout the entire length thereof by said rotary metal removal toolto produce a finished bore.

5. The method of claim 4 including the step of directing a source ofbeam energy to said beam machining tool; and directing and focussingsaid beam from said beam machining tool to said workpiece.

6. The method of claim 5 including the step of imparting rotation tosaid tools during the machining operations.

7. A method of forming a finished diameter bore in a difficultymachinable workpiece, comprising; simultaneously forming an undersizebore in said workpiece and producing a physically altered zonesurrounding said undersize bore by beam machining said workpiece; andthen concomitantly enlarging said undersize bore and removing said zonethroughout the entire length thereof by a rotary workpiece removaloperation to produce said finished diameter bore.

8. The method of claim 7 wherein said beam machining consists of lasermachining.

9. The method of claim 7 wherein said beam machining consists ofelectron beam machining.

10. A method of machining a difficulty machinable workpiece, comprising;positioning a beam machining tool on a fixed tool support adjacent saidworkpiece; beam machining said workpiece along a centerline tosimultaneously form an undersize bore and a physically altered zonesurrounding said undersize bore; substituting a rotary workpiece removaltool on said fixed tool support for said beam machining tool; andmechanically machining said workpiece along said centerline toconcomitantly enlarge said undersize bore and remove said zone zonethroughout the entire length thereof by said rotary workpiece removaltool to produce a finished bore.

11. The method of claim 10 including the step of directing a source ofbeam energy to said beam machining tool; and directing and focussingsaid beam from said beam machining tool to said workpiece.

12. The method of claim 11 including the step of imparting rotation tosaid tools during the machining operations.

1. A method of forming a finished diameter bore in a metallic workpiece,comprising; simultaneously forming an undersize bore in said workpieceand producing a metallurgically altered zone surrounding said undersizebore by beam machining said workpiece; and then concomitantly enlargingsaid undersize bore and removing said zone throughout the entire lengththereof by a rotary metal removal operation to produce said finisheddiameter bore.
 2. The method of claim 1 wherein said beam machiningconsists of laser machining.
 3. The method of claim 1 wherein said beammachining consists of electron beam machining.
 4. A method of machininga workpiece, comprising; positioning a beam machining tool on a fixedtool support adjacent a metallic workpiece; beam machining saidworkpiece along a centerline to simultaneously form an undersize boreand a metallurgically altered zone surrounding said undersize bore;substituting a rotary metal removal tool on said fixed tool support forsaid beam machining tool; and mechanically machining said workpiecealong said centerline to concomitantly enlarge said undersize bore andremove said zone throughout the entire length thereof by said rotarymetal removal tool to produce a finished bore.
 5. The method of claim 4including the step of directing a source of beam energy to said beammachining tool; and directing and focussing said beam from said beammachining tool to said workpiece.
 6. The method of claim 5 including thestep of imparting rotation to said tools during the machiningoperations.
 7. A method of forming a finished diameter bore in adifficulty machinable workpiece, comprising; simultaneously forming anundersize bore in said workpiece and producing a physically altered zonesurrounding said undersize bore by beam machining said workpiece; andthen concomitantly enlarging said undersize bore and removing said zonethroughout the entire length thereof by a rotary workpiece removaloperation to produce said finished diameter bore.
 8. The method of claim7 wherein said beam machining consists of laser machining.
 9. The methodof claim 7 wherein said beam machining consists of electron beammachining.
 10. A method of machining a difficulty machinable workpiece,comprising; positioning a beam machining tool on a fixed tool supportadjacent said workpiece; beam machining said workpiece along acenterline to simultaneously form an undersize bore and a physicallyaltered zone surrounding said undersize bore; substituting a rotaryworkpiece removal tool on said fixed tool support for said beammachining tool; and mechanically machining said workpiece along saidcenterline to concomitantly enlarge said undersize bore and remove saidzone zone throughout the entire length thereof by said rotary workpieceremoval tool to produce a finished bore.
 11. The method of claim 10including the step of directing a source of beam energy to said beammachining tool; and directing and focussing said beam from said beammachining tool to said workpiece.
 12. The method of claim 11 includingthe step of imparting rotation to said tools during the machiningoperations.